Answer:
[tex]\boxed{\text{252.0 g}}[/tex]
Explanation:
         water ⟶ hydrogen + oxygen
mass/g:      x        28.0     224.0
According to the Law of Conservation of Mass,
[tex]\begin{array}{rcl}\\\text{Mass of reactants} & = & \text{mass of products} \\\text{Mass of water} & = & \text{mass of hydrogen + mass of oxygen} \\x & = & 28.0 + 224.0\\& = & \textbf{252.0 g}\\\end{array}\\\text{The mass of water was $\boxed{\textbf{252.0 g}}$}[/tex]
